We're now hearing from the team that an update is propagating through the Marketplace, enabling 30-way group messaging across iOS, Android, BlackBerry, and Windows Phone devices! (If your friends are still rocking Nokia s40/s60 devices, they have to wait a little longer.)

eBuddy XMS is a free app that you can find here at the Windows Phone Marketplace. We haven't gotten our hands on the update yet, but if you have, share your thoughts in the comments or on our forums.